1. Field of the Invention
The present invention generally relates to an image processing technique, and more particularly, to an image compression technique wherein a luminance information Y and a color information Cb and/or Cr are respectively filtered.
2. Description of Related Art
A more effective image processing technique is required due to the development of digital cameras in recent years. Usually, a user has to take a digital color photo with low luminance in order to achieve an anti-shake effect. As a result, the requirement to the noise reduction performance at high ISO value is increased. Generally speaking, the lower the ISO value is, the less noise is produced, and the higher the ISO value is, the more noises are produced. Thereby, how to suppress image noises, especially color noises, produced by high ISO value has become a major subject in the industry.
Generally speaking, a digital image processor should have at least a sensor interface module, an image pipeline module, a scalar module, and a JPEG module to process a digital photo. The digital photo can be converted into a compressed image file through the operations of these modules.
Generally speaking, an image output by a sensor is a pixel array in a RGGB Bayer pattern or CMYG pattern. The image is first converted by the image pipeline module into a RGB image and then an YCbCr image. After that, the image is resized by the scalar module and then compressed by the JPEG module into a JPG file.
However, in the conventional image processing technique, the luminance noise and color noise in the image are not effectively suppressed.